linux-kernel - [PATCH v4 1/3] riscv: Improve PTDUMP to show RSW with non-zero value

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Message-ID: <20230921025022.3989723-2-peterlin@andestech.com>
Date:   Thu, 21 Sep 2023 10:50:20 +0800
From:   Yu Chien Peter Lin <peterlin@...estech.com>
To:     <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <david@...hat.com>,
        <akpm@...ux-foundation.org>, <alexghiti@...osinc.com>,
        <bjorn@...osinc.com>, <linux-riscv@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     <conor.dooley@...rochip.com>,
        Yu Chien Peter Lin <peterlin@...estech.com>
Subject: [PATCH v4 1/3] riscv: Improve PTDUMP to show RSW with non-zero value

RSW field can be used to encode 2 bits of software
defined information. Currently, PTDUMP only prints
"RSW" when its value is 1 or 3.

To fix this issue and improve the debugging experience
with PTDUMP, we redefine _PAGE_SPECIAL to its original
value and use _PAGE_SOFT as the RSW mask, allow it to
print the RSW with any non-zero value.

This patch also removes the val from the struct prot_bits
as it is no longer needed.

Signed-off-by: Yu Chien Peter Lin <peterlin@...estech.com>
Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
Tested-by: Alexandre Ghiti <alexghiti@...osinc.com>
---
Changes v1 -> v2
- Redefine _PAGE_SPECIAL to (1 << 8)
Changes v2 -> v3
- Add commet for _PAGE_SPECIAL
- Add ".." when RSW field is clear
- Fix unbalanced braces warning
Changes v3 -> v4
- Include Alexandre's RB/TB-tags
---
 arch/riscv/include/asm/pgtable-bits.h |  4 +--
 arch/riscv/mm/ptdump.c                | 35 ++++++++++++---------------
 2 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
index f896708e8331..179bd4afece4 100644
--- a/arch/riscv/include/asm/pgtable-bits.h
+++ b/arch/riscv/include/asm/pgtable-bits.h
@@ -16,9 +16,9 @@
 #define _PAGE_GLOBAL    (1 << 5)    /* Global */
 #define _PAGE_ACCESSED  (1 << 6)    /* Set by hardware on any access */
 #define _PAGE_DIRTY     (1 << 7)    /* Set by hardware on any write */
-#define _PAGE_SOFT      (1 << 8)    /* Reserved for software */
+#define _PAGE_SOFT      (3 << 8)    /* Reserved for software */
 
-#define _PAGE_SPECIAL   _PAGE_SOFT
+#define _PAGE_SPECIAL   (1 << 8)    /* RSW: 0x1 */
 #define _PAGE_TABLE     _PAGE_PRESENT
 
 /*
diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c
index 20a9f991a6d7..57a0926c6627 100644
--- a/arch/riscv/mm/ptdump.c
+++ b/arch/riscv/mm/ptdump.c
@@ -129,7 +129,6 @@ static struct ptd_mm_info efi_ptd_info = {
 /* Page Table Entry */
 struct prot_bits {
 	u64 mask;
-	u64 val;
 	const char *set;
 	const char *clear;
 };
@@ -137,47 +136,38 @@ struct prot_bits {
 static const struct prot_bits pte_bits[] = {
 	{
 		.mask = _PAGE_SOFT,
-		.val = _PAGE_SOFT,
-		.set = "RSW",
-		.clear = "   ",
+		.set = "RSW(%d)",
+		.clear = "  ..  ",
 	}, {
 		.mask = _PAGE_DIRTY,
-		.val = _PAGE_DIRTY,
 		.set = "D",
 		.clear = ".",
 	}, {
 		.mask = _PAGE_ACCESSED,
-		.val = _PAGE_ACCESSED,
 		.set = "A",
 		.clear = ".",
 	}, {
 		.mask = _PAGE_GLOBAL,
-		.val = _PAGE_GLOBAL,
 		.set = "G",
 		.clear = ".",
 	}, {
 		.mask = _PAGE_USER,
-		.val = _PAGE_USER,
 		.set = "U",
 		.clear = ".",
 	}, {
 		.mask = _PAGE_EXEC,
-		.val = _PAGE_EXEC,
 		.set = "X",
 		.clear = ".",
 	}, {
 		.mask = _PAGE_WRITE,
-		.val = _PAGE_WRITE,
 		.set = "W",
 		.clear = ".",
 	}, {
 		.mask = _PAGE_READ,
-		.val = _PAGE_READ,
 		.set = "R",
 		.clear = ".",
 	}, {
 		.mask = _PAGE_PRESENT,
-		.val = _PAGE_PRESENT,
 		.set = "V",
 		.clear = ".",
 	}
@@ -208,15 +198,20 @@ static void dump_prot(struct pg_state *st)
 	unsigned int i;
 
 	for (i = 0; i < ARRAY_SIZE(pte_bits); i++) {
-		const char *s;
-
-		if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val)
-			s = pte_bits[i].set;
-		else
-			s = pte_bits[i].clear;
+		char s[7];
+		unsigned long val;
+
+		val = st->current_prot & pte_bits[i].mask;
+		if (val) {
+			if (pte_bits[i].mask == _PAGE_SOFT)
+				sprintf(s, pte_bits[i].set, val >> 8);
+			else
+				sprintf(s, "%s", pte_bits[i].set);
+		} else {
+			sprintf(s, "%s", pte_bits[i].clear);
+		}
 
-		if (s)
-			pt_dump_seq_printf(st->seq, " %s", s);
+		pt_dump_seq_printf(st->seq, " %s", s);
 	}
 }
 
-- 
2.34.1